Ultraviolet (UV) therapy, also called phototherapy or light therapy, is a type of treatment that uses UV light rays on affected areas of skin. This type of treatment is thought to help stop skin cells from growing too quickly.

Dermatologists usually use two kinds of UV light: ultraviolet A (UVA) and ultraviolet B (UVB). These treatments are done in the doctor’s office using a special light box that exposes the entire body, one side of the body, or limited areas to UV rays for a period of time.

UVB phototherapy for psoriasis

Ultraviolet B (UVB) therapy is often recommended for people with psoriasis who have plaques that cover large areas of their body. Most people get two to four UV phototherapy treatments per week. The exact dose is based on each person’s needs. Your dermatologist may decide to combine UVB treatments with topical or systemic treatments to get better or faster results, or to help limit side effects by lowering the number of treatments and/or doses of the medicines.

There are two types of UVB treatment, broad band and narrow band. They are similar in many ways. The major difference between them is that narrow band UVB light bulbs release a smaller amount of UV light.

PUVA phototherapy for psoriasis (pronounced "poova")

PUVA (psoralen ultraviolet A) combines UVA treatment with psoralen, a medicine that makes the skin more sensitive to UV light. Psoralen can be in the form of a pill, cream, lotion, ointment, or water bath solution. Patients take the psoralen one to three hours before going inside the UVA light box. The amount of time spent under the lights depends on skin type (the darker or more tan you are, the more time it will take). It takes about 20 phototherapy treatments to see skin clearing.

Important information you should know

All medicines have potential side effects and should be used cautiously and under the supervision of a healthcare professional. Some common adverse events associated with UV phototherapy include skin irritation, light sensitivity, and burning. Long-term PUVA treatment in Caucasians is associated with an increased risk of skin cancer.